Add VTS for new API for clearing buffer slots

Bug: 262041682
Bug: 258196272
Test: VtsHalGraphicsComposer3_TargetTest
Change-Id: If7e5fea56734f3ae7b4aae7378f4aea0eacc8e32
diff --git a/graphics/composer/aidl/vts/VtsComposerClient.h b/graphics/composer/aidl/vts/VtsComposerClient.h
index 1883336..e61fde9 100644
--- a/graphics/composer/aidl/vts/VtsComposerClient.h
+++ b/graphics/composer/aidl/vts/VtsComposerClient.h
@@ -61,6 +61,8 @@
 
     bool tearDown();
 
+    std::pair<ScopedAStatus, int32_t> getInterfaceVersion();
+
     std::pair<ScopedAStatus, VirtualDisplay> createVirtualDisplay(int32_t width, int32_t height,
                                                                   PixelFormat pixelFormat,
                                                                   int32_t bufferSlotCount);